Driving over the summit on Hwy 17 after diving

[Ricky B]

Monterey is easily accessible by car from the SF Bay Area, and I assume a number of divers drive to Monterey, go diving for the day, and drive home. Going from Monterey to the SF Bay Area, I would end up driving up Hwy 17 and going over what is called "the summit." The summit has an altitude of 1800 feet. Monterey is, of course, at sea level. Thus, driving over the summit is no different from flying at 1800 feet in an unpressurized cabin.

What's the protocol here?

Is 1800 feet low enough that it's not a concern.

Is a couple of hours enough before going over the summit a sufficient interval?

OK, I'm sure that one should calculate the residual nitrogen per the NOAA tables and then consult the NOAA ascent-to-altitude table, but is that what you do?

Are there regular dive commuters to and from Monterey who go over the summit?

 

[Fundive123]

Monterey is easily accessible by car from the SF Bay Area, and I assume a number of divers drive to Monterey, go diving for the day, and drive home. Going from Monterey to the SF Bay Area, I would end up driving up Hwy 17 and going over what is called "the summit." The summit has an altitude of 1800 feet. Monterey is, of course, at sea level. Thus, driving over the summit is no different from flying at 1800 feet in an unpressurized cabin.

OK, I'm sure that one should calculate the residual nitrogen per the NOAA tables and then consult the NOAA ascent-to-altitude table, but is that what you do?

I drive from the bay area to Monterey and back to do dives, but I can and do avoid highway 17. To get there instead of going through Santa Cruz I take 680S to 101S to 156W, then highway 1.

 

[TSandM]

When you consider the time it takes to get out of the water, pack your gear, get in the car, and drive to the summit, I think it's highly unlikely that ascending to that altitude in that period of time creates much risk.

I dive and drive over a 3000 foot pass. I'll admit, they aren't technical dives, nor do I typically push NDLs.

 

[underH2Oman]

This is what NOAA says.
http://www.ndc.noaa.gov/pdfs/AscentToAltitudeTable.pdf

I getting older would wait longer than they say but thats me.

 

[TSandM]

Of course, generally, none of us who dive computers really know what our pressure groups are . . .

 

[flyandive]

Well, I just did a dive to 200ft for 20 minutes with 55 minutes of deco yesterday then drove home via that very highway (I forgot about the 1800ft change in elevation) and well, I'm still here. Disclaimer: Your results may differ.

 

[GregSaiz]

For some reason, I always prefer to drive highway 17 en route to Monterey and take 101 home. Great, now I can justify it!
Good post - I'd never given much though to the highway 17 altitude change but in the future, if I'm doing a deco profile, it might just pay to be more conservative on the drive home. Well, except on a Sunday - 101 traffic on a Sunday afternoon might be worse than a mild hit.

 

[drbill]

Obviously no one can really say if it is 100% safe for you, only suggest the odds. We had a local dive instructor here on Catalina who did several shallow training dives one day, drove to her boyfriend's house over a 1,600 ft elevation and got bent. Just one example of what I would have thought was fairly safe... but wasn't.

 

[GrumpyOldGuy]

This is what NOAA says.
http://www.ndc.noaa.gov/pdfs/AscentToAltitudeTable.pdf

I getting older would wait longer than they say but thats me.

I use the NOAA table when planning a return flight that is under 24 hours. Be aware, although it is a great tool, you must use the NOAA tables. The letter groups from PADI are not the same, thus is the NOAA is useless for PADI tables. The NOAA tables are free and available, you have to use them.

If you want a general feel and diving a computer. Take your max depth and then cross reference it to the NOAA NDL limit for that depth. This should give you the worse case scenario and an upper limit of what you should do.

FWIW: Generally it is pretty hard to get yourself in trouble with ascents less than 2000' on NORMAL dives. With many repetitive dives or odd profiles, it is hard to tell unless you compare it to the NOAA tables or some other objective standard.

 

[zf2nt]

I took 17 home every day for the 7 years that I operated Aquarius and still use it when I go to Monterey. I calculated that it is 13 miles shorter for me in Saratoga to take 17 than to go on 101, so it does save me time. The scenery is lots better, and after a while you know every place on 17 the CHP likes to hide. If you've been out of the water for a while, the 1800' at Patchen Pass is not an issue.